Projected flood water depths on Roi-Namur, Kwajalein Atoll, Republic of the Marshall Islands

Projected future wave-driven flooding depths on Roi-Namur Island on Kwajalein Atoll in the Republic of the Marshall Islands for a range of climate-change scenarios. This study utilized field data to calibrate oceanographic and hydrogeologic models, which were then used with climate-change and sea-level rise projections to explore the effects of sea-level rise and wave-driven flooding on atoll islands and their freshwater resources. The overall objective of this effort, due to the large uncertainty in future emissions (and thus climate change scenarios) that is largely irreducible, was to reduce risk and increase island resiliency by providing model simulations across a range of plausible future conditions. This effort focuses on Roi-Namur Island on Kwajalein Atoll in the Republic of the Marshall Islands (RMI). RMI is home to more than 1,100 low-lying islands on 29 atolls, yet the approach and findings presented in this study can serve as a proxy for atolls around the world, most of which have a similar morphology and structure, including on average, even lower land elevations, and are the home for numerous island nations and hundreds of thousands of people. The primary goal of this investigation was to determine the influence of climate change and sea-level rise on wave-driven flooding and the resulting impacts to infrastructure and freshwater resources on atoll islands. First, we mapped the morphology and benthic habitats of the atoll to determine the influence of spatially-varying bathymetric structure and hydrodynamic roughness on wave propagation over the coral reefs that make up the atoll. Second, we analyzed historic meteorologic and oceanographic data to provide historical context for the limited in-situ data and comparison to previous seawater overwash and flooding events. These data were then used to calibrate and validate physics-based, dynamically-downscaled numerical models to project future atmospheric and oceanic forcing for a range of climate-change scenarios. Third, we made in-situ observations to better understand how changes in meteorologic and oceanographic forcing controlled wave-driven water levels, seawater flooding of the island, and the resulting hydrogeologic response. We then used those data to calibrate and validate a physics-based, numerical hydrodynamic model of the island. The hydrodynamic model was used to forecast future wave-driven island overwash and seawater flooding for a range of climate-change and SLR scenarios. The data provided here are the seawater flooding depths for three Intergovernmental Panel on Climate Change (IPCC) AR5 climate-change scenarios: Representative Concentration Pathways (RCP)4.5 and RCP8.5, representing medium and high greenhouse concentration trajectory scenarios, respectively, and RCP8.5 plus icesheet collapse (RCP8.5i). The climate-change scenarios were incorporated into the model by increasing mean sea level based on the future sea-level rise and wave projections. The modeled time frame ranged from 2035 to 2105 at 10-yr time steps. These data accompany the following publication: Storlazzi, C.D., Gingerich, S.B., van Dongeren, A., Cheriton, O.M., Swarzenski, P.W., Quataert, E., Voss, C.I., Field D.W., Annamalai, H., Piniak G.A., McCall, R., 2018, Most atolls will be uninhabitable by the mid-21st century due to sea-level rise exacerbating wave-driven flooding, Science Advances, https://doi.org/XXX.

针对一系列气候变化情景，马绍尔群岛共和国夸贾林环礁的罗伊-纳穆尔岛未来由波浪驱动的洪水淹没深度预测数据。本研究利用野外实测数据对海洋学与水文地质模型进行率定，随后结合气候变化与海平面上升预测结果，探究海平面上升及波浪驱动型洪水对环礁岛屿及其淡水资源的影响。鉴于未来碳排放（进而气候变化情景）存在极大且基本无法降低的不确定性，本研究的核心目标是通过构建一系列合理未来情景下的模型模拟结果，降低灾害风险并提升岛屿韧性。本次研究聚焦于马绍尔群岛共和国（Republic of the Marshall Islands, RMI）夸贾林环礁的罗伊-纳穆尔岛。马绍尔群岛共和国拥有分布于29个环礁之上的1100余个低洼岛屿，而本研究采用的研究方法与所得结论可作为全球环礁的参照范本——全球多数环礁具有相似的地貌与结构特征，平均海拔甚至更低，且为数个岛国及数十万民众提供栖居之所。本研究的主要目标是明确气候变化与海平面上升对波浪驱动型洪水的影响，以及由此对环礁岛屿的基础设施与淡水资源造成的冲击。其一，绘制该环礁的地貌与底栖生境分布图，以明确空间异质性的水深地形结构与水动力粗糙度对构成环礁的珊瑚礁上的波浪传播过程的影响；其二，分析历史气象与海洋学数据，为有限的原位实测数据提供历史背景参照，并与过往的海水漫溢与洪水事件进行对比；随后利用这些数据对基于物理过程的动力降尺度数值模型进行率定与验证，以针对一系列气候变化情景预测未来的大气与海洋强迫场。其三，开展原位观测，以更深入地理解气象与海洋强迫场的变化如何调控波浪驱动的水位、岛屿海水漫溢以及由此产生的水文地质响应；随后利用这些数据对基于物理过程的岛屿水动力数值模型进行率定与验证。该水动力模型被用于针对一系列气候变化与海平面上升（Sea Level Rise, SLR）情景，预测未来岛屿的波浪驱动型漫溢与海水洪水过程。本次提供的数据为三种政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, IPCC）第五次评估报告（AR5）气候变化情景下的海水淹没深度，分别为典型浓度路径（Representative Concentration Pathways, RCP）4.5与RCP8.5（分别代表中等与高强度温室气体排放情景），以及叠加冰盖崩塌情景的RCP8.5（RCP8.5i）。本研究通过基于未来海平面上升与波浪预测结果抬升平均海平面的方式，将气候变化情景嵌入模型之中。模型模拟的时间范围为2035年至2105年，时间步长为10年。本数据集配套发表论文如下：Storlazzi, C.D.等, 2018年, 《因海平面上升加剧波浪驱动型洪水，多数环礁至21世纪中叶将不再适宜居住》, 《Science Advances》, https://doi.org/XXX。